The present invention relates to a soundboard for string instruments, especially pianos, harpsichords, or the like.
Percussive string instruments, such as pianos or grand pianos, are known to be equipped with resonators having plate-shaped soundboards, which function to transmit the vibrations of the string to the air while at the same time increasing the sound emission or volume. In conventional constructions, the soundboards are made from solid wood, preferably from especially grown and selected conifers, such as fir, spruce, pine or hemlock. However, due to the reduction in the conifer stock, it has become more and more difficult to find suitable woods having the necessary qualities for the making of soundboards. The known soundboards made from solid boards are very susceptible to varying relative air humidity, by which the interior stresses are subject to continuous changes, in particular at the beginning and the end of indoor heating periods. Such stress will interfere also with the inner vibration conditions of the soundboard so that, when the vibrations of the strings are transmitted to the air, the transmission characteristics are subjected to undesirable change.
In order to avoid the aforementioned difficulties, soundboards have been made from plastic materials which, it is true, offer the advantage of being less affected by temperature and humidity variations, but lead to unsatisfactory results due to excessive damping, especially in the high frequencies.
It is a known fact that in order to obtain good transmission characteristics, it is desirable that, in the entire audible frequency range, the ratio of the modulus of elasticity to the density of the soundboard should be as great as possible. As far as the inherent characteristics of wood and also plastic materials are concerned, such ratio can, only to a slight extent, be influenced by an adequate selection of the type of wood or of the composition of the plastic material. Therefore, because of the inherent damping of wood materials as well as plastic material, the transmission characteristic of vibrations of high frequencies are unfavorably affected.
It is the object of the present invention to construct a soundboard where, in addition to its being substantially uninfluenced by humidity and heat variations, the damping of the vibrations transmitted is kept at as low a level as possible, thereby resulting in an increase of the sound release in the entire frequency range in question. It is a further object to provide a construction wherein it is possible to exert a selective influence on the degree of damping.